Bath for galvanic production of magnetically high-grade coatings



solution is adjusted to 4.5 with acid or alkali.

United States Patent Ofiice 3,690,734 Patented May 21, 1963 Claims priority, application Germany Nov. 19, 1960 3 Claims. (Cl. 204-48) The magnetic properties of electrolytic metal deposits are known to be improved by certain additives, such as alkali metal thiocyanate and alkali metal hypophosphite.

The object of the invention is a bath for galvanic production of magnetically high-grade coatings, characterized by containing trimethylborazane. Such baths are, e.g.: iron. nickel and cobalt baths, the metal salt concentrations of which can vary. A trimethylborazane content in small amounts of e.g. 0.1 g./l. to 10 g./l., preferably 0.5 g./l. to 4 g./l., in such baths, act to raise the remanence by about 50%. At the same time it acts as a brilliance additive. Moreover, it is possible in this way to approach so far the ideal rectangular hysteresis loop that the measured remanence reaches about 80 to 95% of saturation magnetization. A further advantage of the trimethylborazane content in galvanic baths, which produce magnetic deposits themselves, consists in that it is not necessary to use particular bath concentrations, but the metal salt concentrations can be widely varied, without the action of the trimethylborazane being significantly affected.

In order to be able to measure the hysteresis loop of magnetic coatings, synthetic resin foils of constant surface were subjected to chemical plating. To the magnetically indifferent but electrically conductive layer thus obtained, a magnetic coating was galvanically applied.

The magnetic values: coercive power, remanence and measured remanence/saturation magnetization, were obtained as relative values by comparison with an iron oxide tape (normal commercial sound tape). The iron oxide tape possesses the following values: Coercivity: 300; remanence=850; measured remanence/saturation=0.82. The following examples are given for the purpose of illustrating the invention.

Example I (a) In a galvanic bath with 100 g./l. cobalt sulphate, a chemically plated synthetic resin toll is suspended, measuring 50 x 60 mm. The anode consists of nickel; the anode gap is 8 cm. The pH-value of the aqueous A direct current of 0.5 A. is passed for 8 minutes at a bath temperature of 40 C.

(b) Operation as in (a) is carried out in a bath with 100 g./l. cobalt sulphate and 2 g./l. trimethyl borazane.

The following magnetic values were found:

The same results are obtained when replacing the cobalt salt by a nickel salt.

Example 2 In a galvanic bath with 100 g./l. cobalt chloride, 100 ./l. nickel chloride and 50 g./1. ammonium chloride, alvanizing is carried out as in Example 1.

By adding 0.5 g./l., 0.75 g./l., 1.0 g./l. and 2.0 g./l. of trimethyl-borazane, the following magnetic values are obtained.

V Measured Tmncthylhorazane Content, (Joerclvity Rclnanencel rcinanonce/ gJl. 100 mg. saturation magnetization Analogous results are obtained when using one metal salt only.

Example 3 In a galvanic bath with 50 g./l. ferrous sulphate, 50 g./l. cobalt chloride, 25 g./l. nickel chloride and 50 g./l. ammonium chloride, galvanizing is carried out as described in Example 1.

By adding 1.0 g./l., 2.0 g./l., 3.0 g./l. and 3.5 g./l. trimethyl-borazane, the following magnetic values are obtained.

Analogous results are obtained when using one metal salt only.

We claim:

1. A bath for electrolytic disposition of films having improved magnetic properties, comprising an aqueous solution of a salt of a metal selected from the group consisting of iron, cobalt, and nickel, and, as an additive to provide said improvement, 2. small but effective amount of trimethylborazane.

2. A bath according to claim 1, the trimethylborazane being present in amount of 0.1-10 g./l.

3. A bath according to claim 1, the trimethylborazaue being present in amount of 0.5-4.0 g./l.

No references cited. 

1. A BATH FOR ELECTROLYTIC DISPOSITION OF FILMS HAVING IMPROVED MAGNETIC PROPERTIES, COMPRISING AN AQUEOUS SOLUTION OF A SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF IRON, COBALT, AND NICKEL, AND, AS AN ADDITIVE TO PROVIDE SAID IMPROVEMENT, A SMALL BUT EFFFECTIVE AMOUNT OF TRIMETHYLBORAZANE. 